1. Field of the Invention
This invention relates to a method for the prediction and subsequent confirmation of ovulation during the menstrual cycle of the human female. More specifically, the invention relates to a method and apparatus for the accurate discrimination of the fertile phase from the non-fertile phase of the menstrual cycle of the human female.
2. Description of the Prior Art
The need for a simple but reliable method of predicting and confirming ovulation, which is conveniently carried out in the privacy of the home, has been a recognized need for many decades. Because of religious, philosophic, or health considerations, the preferred method of birth control for many is by periodic abstinence, also known as the "rhythm method." This method involves the identification of the fertile period using an available method, or more often simply by a guess based on the length of the menstrual cycle, and then avoiding coitus during this period. Ovulation is assumed to occur mid-cycle, and the period of abstinence is adjusted accordingly. This technique has proven highly unreliable at best. The unreliability of the rhythm method is largely due to the inability to accurately predict and confirm ovulation. Thus, a clear need exists for a natural family planning method with improved reliability.
A more reliable procedure, known as the sympto-thermal method, involves a subjective evaluation of basal body temperature and cervical mucus to determine the fertile period. This method requires intensive user training in the method and relatively high failure rates were and are still unavoidable.
In another procedure, changes in cervical mucus are combined with basal body temperature (BBT) to identify the onset and end of the fertile period. There are several disadvantages with this approach, some of them being the need for immobility before taking the temperature, daily monitoring of the cervix and vagina, and subjective interpretation of vaginal mucus quality and of the BBT trend. The technique is difficult to learn, with one to six months of careful training and supervision being required to acquire proficiency. Another relatively serious problem is the variation of the relation between the basal body temperature and the peak mucus symptom. In one study, in twenty-five of the cases, the temperature rise occurred more than 2 days before or 2 days after the peak symptom. Liskin, L. A., "Population Reports," Vol. 9, No. 4, pp. 33-65, Sept. 1981. Furthermore, basal body temperature reflects ovulation in only about 70% of the cycles, since monophasic (non-indicative) basal body temperature curves are frequently seen in ovulatory cycles. Bauman, J. E., "Fertility and Sterility," Vol. 36, pp. 729-733, Dec. 1981. When used for birth control, failure rates of up to 34% have been recorded with this method. Although computerized interpretation of data is now available for the sympto-thermal method as disclosed in U.S. Pat. No. 4,151,831, issued May 1, 1979, to R. W. Lester for "Fertility Indicator" and in published PCT Patent Application Pub. No. WO 83/01735, published May 29, 1983, on an application filed Sept. 30, 1982, by H. Schneider, for "Apparatus and Method for Determining Fertility Status", the disadvantages inherent in the physiological parameters used in the method are still limiting factors.
The identification of a preovulatory rise in estrogens followed by a peak in luteinizing hormone (LH) concentration as determined by radioimmunoassay is a good indication of imminent ovulation. Frequently, several samples of blood, drawn at mid-cycle, will be analyzed for luteinizing hormone concentration. These techniques are expensive and require several visits to a hospital or medical laboratory having the appropriate analytical facilities.
The process of ovulation can also be monitored and detected using ultrasonography. Daily visits to a center equipped with the sophisticated instrumentation used for the procedure are necessary. Several scans are required by mid-cycle to pinpoint ovulation by observing follicular development and subsequent ovum release. While accurate identification of ovulation is possible with this technique, it is of little value as a self-monitoring method for purposes of enhancing or reducing fertility.
Several methods of predicting ovulation based on biochemical changes in various body fluids such as vaginal secretions, saliva, or urine have been proposed. The major drawback of such methods is the significant variation in the component being measured between individuals. In one method, where the lactic acid concentration of vaginal secretions was proposed as an indicator of impending ovulation, the variability of its concentration between individuals was as great as one thousand percent. See U.S. Pat. No. 4,010,738, issued Mar. 8, 1977, to G. Preti et al., for "Method of Predicting and Detecting Ovulation."
As a practical matter, it is generally believed at the present time to be impossible to design a chemical indicator system that is applicable to all women. One example of such a problem is related to the alkaline phosphatase levels of saliva which, although appearing to be predictive of ovulation, show such variations among individuals that any chemical means of monitoring for its changes requires that tests be individually calibrated to each user. See U.S. Pat. No. 3,406,005, issued October, 1968 to Foster. Methods based on analysis of urine for steroid hormones or their derivatives are subject to the same problem.